The subject invention relates to a smoothing, cutting and polishing tool for use in the field of denistry, for work by dental technicians, in jewelry making, in tool manufacture and in various other fields and applications.
Tools of this type typically have a smoothing, grinding, cutting and polishing disc attached thereto. Particularly in the field of dentistry, devices for carrying such discs are often referred to as mandrels, and serve to provide a rigid mounting device for smoothing discs made of grinding cloth, felt, rubber, leather or synthetic materials. In the publication Dental-Dienst, No. 2/81, p.p. 18-26, an assortment of such smoothing discs and disc-carrying devices is presented, but the various embodiments distinguish themselves from each other essentially only by the manner in which the discs are mounted.
According to a first form, the disc-carrying device is axially bored and provided with an internal thread. The disc is fastened to the top of the disc-carrying device by means of a washer and a screw. In addition the cited publication points out that, "A well tightened screw as well as a flawless handle to which a carrier is fastened up to the top guarantee a long functional lifetime and safe working conditions." In polishing and smoothing procedures in dental offices and dental laboratories such devices are used with a rate of up to 85 000 rpm.
It is known that for dental work these devices are designed for rotation in both directions. Accordingly, in order to avoid the loosening of the threaded connection at revolutions, their internal threads and screws are provided with both a right handed and left handed version.
Such a fastening process is time consuming and requires the screw to be driven in, in order to provide for a secure tightening thereof.
For a separating disc quick mount, particularly for discs made of paper or nylon, a disc-carrying device bored in an axial direction has been proposed, equipped with points and at a free end of the head, with a clamp holder consisting of a plate for the purpose of pressing on a disc and a multiply bent shaft, maintaining itself by virtue of the resiliency due to the bending in the boring of the disc carrier. For this fastening type, use of the tool at the usual high revolutions, but with only slight lateral pressure, is recommended.
A similar fastening mode is effected by means of a head with an axial slit and a wedge shaped insert. Those two forms require substantial skill by the dentist, since the discs could break under the required contact pressure. In addition it is known that this carries a danger of possible injury to the dentist, particularly to his or her fingers.
The holes in the discs are frequently reinforced by eylets of square or round opening. This raises difficulties in the manufacturing process, since the high number of revolutions requires a precise centering of the eyelets. Furthermore, unvoidable mostly dark discolorations occur in the areas touched by such metallic core during the process of smoothing or polishing of fillings or surfaces of a tooth.
Since the flying off of a disc could be lethal to a patient, a good fastening device is imperative as demonstrated in an article in "Tandelaegebladet," Vol. 1980:84:No. 13:5379.